Manufacture of dental bridgework



Oct. 1965 E. E. SCHWARZ MANUFACTURE OF DENTAL BRIDGEWORK 2 Sheets-Sheet 1 Filed Nov. '7. 1961 INVENTOR fUGE/VE F. SCAN/16422 BY l ATTORNEY 2 Sheets-Sheet 2 mm Z i ,,F 1 E p m s% %m WNW WN MN I E mm mm ww x MN 4% W w. m w ,m

Oct. 5, 1965 E. E. SCHWARZ MANUFACTURE OF DENTAL BRIDGEWORK Filed Nov. 7, 1961 United States Patent 3,210,444 MANUFACTURE OF DENTAL BREDGEWORK Eugene E. Schwarz, 115 Chapman Place, Irvington, NJ. Filed Nov. 7, 1961, Ser. No. 150,743 8 Claims. (Cl. 26416) This invention relates to manufacture of dental bridgework and the like from plastic molding compounds such as acrylics.

Heretofore the flasks containing the molded dentures have been cured by immersion in hot water at atmospheric pressure. The low temperature and pressure have resulted in soft, porous dentures which, in course of time, become discolored by absorption of moisture and stain. These soft porous dentures have required opaques for masking the gold backing to prevent a dull appearance of the freshly cured denture.

It is therefore the main object of the present invention to increase the density of the denture produced. This is accomplished largely by the use of dry heat at temperatures above the boiling point of water, and curing the molding compound under superatmospheric pressure.

Furthermore, the flasks have been constructed of parts hinged together, which have been unwieldy in manipulation, and difficult to retain in precision alignment, resulting in imperfect molding, and leakage further contributing to low density dentures. The expansion of the metal parts could not be controlled, resulting in loss of detail in the mold, and further contributing to the low density.

Other objects are therefore to avoid the above difficulties, eliminate the need for Opaques, and provide a flask construction to facilitate manipulation, effect precision alignment, avoid leakage, and to apply thermal expansion of metals plus mold swelling to increase the density of the product.

According to the present invention, the flask comprises a cope, drag and cheeks which fit together with a cam action to compress the contents. The filled flask is inserted in a press containing a thermally expansible bellows which is compressed thereby to further compress the flask. The press with the flask therein is inserted into a dry oven or furnace to cure the acrylic denture by dry heat above Water boiling temperature. The expansion of the bellows subjects the flask contents to superatmospheric pressure. The expansion of the metal of the flask and the mold swelling are applied to increase the density of the acrylic denture.

In thedrawings:

FIG. 1 is an assembled front elevation of the apparatus for curing dental bridgework according to the preferred embodiment of the present invention;

FIG. 2 is an exploded front elevation of the flask shown in FIG. 1;

FIG. 3 is a left end elevation of the same; and

FIG. 4 is a right end elevation of the same.

The apparatus shown in FIG. 1 comprises generally a press P, constant pressure units C, and a dental flask F. These parts are preferably of stainless steel.

The press P comprises a rigid frame having a screw in the top to apply pressure on the flask F between a movable jaw 12 and the bottom 14 of the rigid frame.

The constant pressure units C each comprise an outer cup 16 which receives a bellows 18 filled with an expansible fluid such as water. The top of the bellows 18 normally extends above the top of the rim of the cup 16.

The cups 16 of the units C rest on the bottom 14 of the press, the flask 14 is interposed thereabove and rests thereon below the jaw 12, and the screw 10 is tightened to compress the bellows 18 until the bottom of the flask 14 abuts the rim of the cup 16. When subjected to dry heat curing, the fluid in the bellows 18 expands with degrees of Fatented Dot. 5, 1965 temperature and produces superatmospheric pressures up to 1000 pounds per square inch gauge.

As shown in FIGS. 2, 3 and 4, the bottom of the flask F comprises a base or drag 22 of generally channel shape with a flat rectangular floor, having upstanding sides 24 with inner flanges 25 and vertical outer side shoulders 26. The upper side parts of these shoulders form wedge-like inclined surfaces 27, which are slanted to converge upward toward each other into a flat horizontal central shoulder 33. The base 22 also has end rims 28, the right hand end of which has a recess 30. The base also has an access opening 29 to facilitate removal of the arch platform 31 shown in FIG. 1, which fits inside the sides 24 and rims 28 and rests on the floor of the base 22.

The ends or cheeks of the flask F are formed by walls 32 having side flanges 34, the inner vertical edges of which fit over the inner flanges 24 of the base, and abut against the vertical side shoulders 26. The sides 34 have upper parts extending toward each other and having lower surfaces 35 slanted to converge upward, complementary to the base side flange upper surfaces 27. The tops of the side flanges 34 are slanted to converge at. a smaller angle. The walls 32 also have depending lugs 36 which fit inside the base rim 28 when the bottom of the wall 32 abuts the top of the rim 28. The bottom of the right hand end wall has a depending lug 38 which fits into the base rim recess 30.

The top or cope of the flask comprises a flat rectangular roof 40 having 21 depending skirt formed of side walls 42 and end walls 44. The lower rims of the side walls 42 have side portions 46 which converge upwardly complementary to the cheek top 37, to a flat horizontal central rim portion 48, complementary to the flat portion 33 of the base shoulder.

The skirt side walls 44 have depending Wedge portions 50 which enter and engage complementary surfaces of sockets 52 formed in the tops of the cheek end walls 32, to cam them toward each other as the cope is let down thereover. The angle of the cope wedge portions 50 and complementary surfaces 52 is greater than the angle of the drag shoulder portion 27 and complementary surface 35, in turn greater than the angle of the cheek rim surface 37 and complementary surface 46.

In the sequence of steps employing the parts described, the arch platform 31 is installed in the drag, and the 14 unit pattern of plaster of paris with wax teeth is above the arch platform. The cheeks or counter portions 32 are put on and the cavity filled with plaster .of paris or stone composition, overlaid with a separating medium.

The cope or top 40 which has been filled with plaster of paris or stone composition is put on, the wedges 50 camming the cheeks toward each other against the shoulder 26 of the drag.

When the plaster of paris or stone has hardened, the flask is opened and the wax patterns are eliminated, generally by boiling in water to soften the wax which may 'be peeled off. The cavity or void is then filled with acrylic molding composition for example with a spatula, and the cope put on and taken off for test packing and finally put back on. Here the wedging or camming action of the parts of the flask tend to increase the density of the acrylic.

The flask is then put into the press P, with the bellows 18 and the screw 10 is tightened to compress the bellows until the bottom of the drag abuts the rim of cup 16. The press P with the flask and compressed bellows therein is then put into a dry heat oven or furnace and subjected to a temperature considerably above the boiling point of water. With the increasing temperature, the bellows expands and produces superatmospheric pressures up to 1000 pounds per square inch gauge. The wedging or camming actions of the flask parts is compounded with the expansion of the mold and the bellows to compress the acrylic compound throughout the curing process.

It should be noted that in the successive openings of the flask, the parting is along the surface comprising the central horizontals 31-48 and end inclines 37-46 at "both sides thereof. The cheeks may be removed by vertical parting at 3426. But there is never any parting therebetween transverse to the line 31-48, which could mar the front (incisor and canine) units of the 14 unit denture on the arch platform.

What is claimed is:

1. Apparatus for manufacture of dental bridgework, comprising a press having a rigid frame and a movable jaw, an assembled flask in said press between said rigid frame and said movable jaw and having a mold cavity filled with plastic molding compound, said flask being assembled of separate interfitting parts having inclined complementary surfaces, said press serving to clamp said interfitting parts together to cause said inclinedsurfaces to cam the parts therebetween toward each other to compress said molding compound, a bellows containing a thermally expansible fluid and interposed between said rigid frame and said movable jaw and engaging said assembled flask, and means .for subjecting said press, flask and bellows to a temperature above the boiling point of water to cure said plastic molding compound and increase the density thereof.

2. Apparatus for manufacture of dental bridgework, comprising a flask having a mold cavity filled with plastic molding compound, said flask being assembled of separate interfitting inner and outer .parts having inclined complementary surfaces, a press for subjecting said assembled and filled flask to mechanically applied pressure to cause said inclined complementary surfaces to cam said inner parts toward each other and thereby subject said plastic molding compound to superatmospheric pressure, and a dry oven receiving said press with said filled, assembled and pressurized flask to raise the same to a temperature above the boiling point of water to cure said plastic moldin-g compound and combine thermal expansion of the mold with carnming action of said inclined surfaces to increase the density thereof.

3. Apparatus for manufacture of dental bridgework, comprising a flask having a mold cavity filled with plastic molding compound, said flask being assembled of separate interfitting parts comprising a drag, a cope and a pair of complementary cheeks therebetween, certain of said parts having inclined complementary surfaces, said interfitting parts being separable by a rectilinear vertical movement, means for subjecting said assembled and filled flask t clamping action to cause said interfitting parts to cam parts therebetween toward each other under superatmospheric pressure, and means for subjecting said cammed parts to a temperature above the boiling point of water to cure said plastic molding compound and increase the density thereof.

4. Apparatus for manufacture of dental bridgework, comprising a flask having a mold cavity filled with plastic molding compound, said flask being assembled of separate interfitting parts comprising a drag having upstanding sides with vertical shoulders having converging inclined upper portions, a cope having a substantially rectangular top of integral construction from end to end thereof, and cheeks having inclined lower rims complementary to said inclined upper portions of the shoulders of said drag, said interfitting parts being separable by a rectilinear vertical movement, means for subjecting said assembled and filled flask to a clam-ping action to cause said inclined portions cam parts therebetween toward each other to compress said molding compound, and means for subjecting said flask to a temperature above the boiling point of water to cure said plastic molding compound.

5. Apparatus for manufacture of dental bridgework, comprising a flask having a mold cavity filled with plastic molding compound, said flask being assembled of separate interfitting parts comprising a drag, a cope having a substantially rectangular top and a skirt depending therefrom of integral construction from end to end, a side of said skirt having a lower rim inclined upwardly from each end to a central flat portion, and cheeks having upper rims complementary to said inclined surfaces of said cope, said interfitting parts being separable by a rectilinear vertical movement, means for subjecting said assembled and filled flask to a clamping action to cause said inclined portions to cam portions therebetween toward each other to compress said molding compound, and means for subjecting said clamped flask to a temperature above the boiling point of water to cure said plastic molding compound.

6. Apparatus for manufacture of dental bridgework, comprising a flask having a mold cavity filled with plastic molding compound, said flask "being assembled of separate interfitting parts comprising a drag, a cope having a top of integral construction including depending diverging wedge-shaped lugs at the ends thereof, and cheeks having upper sockets with inclined sides complementary to said wedge-shaped lugs, said interfitting parts being separable by a rectilinear vertical movement, means for subjecting said assembled and filled flask to a clamping action to cause said lugs to cam said socket toward each other to compress said molding compound, and means for subjecting said clamped flask to a temperature above the boiling point of water to cure said plastic molding compound.

'7. Method of manufacture of dental bridgework and the like from plastic molding compounds such as acrylic resins, which comprises filling such plastic into the mold cavity above an arch platform in a flask having parts with inclined complementary surfaces, clamping the parts of said flask together to cause said inclined surfaces to cam parts therebetween toward each other to compress said molding compound, and, subjecting said filled and clamped flask to a confined surrounding dry heat source for raising the same to acrylic curing temperature to cause thermal expansion of the flask and swelling of the mold, the clamping pressure being combined with the thermal expansion of the flask and swelling of the mold to compress the plastic throughout the curing process and increase the density of the cured product.

8. Method as claimed in claim '7, in which a bellows containing an expansible fluid is interposed between said flask and said clamp, and the expansion of said bellows is compounded with said mold compressive forces.

References Cited by the Examiner UNITED STATES PATENTS 715,182 12/02 Waegel 1833 723,275 3/03 Hood 1833 824,218 6/06 ToWle 1855.1 1,145,433 7/15 Pappert 1833 2,512,071 6/50 Nolan. 2,887,717 5/59 Smith 264-17 XR 2,896,259 7/59 Harris 1833 2,978,781 4/61 Shuman 2512 1 ALEXANDER H. BRODMERKEL, Primary Examiner.

ROBERT F. WHITE, Examiner. 

1. APPARATUS FOR MANUFACTURE OF DENTAL BRIDGEWORK, COMPRISING A PRESS HAVING A RIGID FRAME AND A MOVABLE JAW, AN ASEEMBLED FLASK IN SAID PRESS BETWEEN SAID RIGID FRAME AND SAID MOVABLE JAW AND HAVING A MOLD CAVITY FILLED WITH PLASTIC MOLDING COMPOUND, SAID FLASK BEING ASSEMBLED OF SEPARATE INTERFITTING PARTS HAVING INCLINED COMPLEMENTARY SURFACES, SAID PRESS SERVING TO CLAAMP SAID INTERFITTING PARTS TOGETHER TO CAUSE SAID INCLINED SURFACES TO CAM THE PARTS THEREBETWEEN TOWARD EACH OTHER TO COMPRESS SAID MOLDING COMPOUND, A BELLOWS CONTAINING A THERMALLY EXPANSIBLE FLLUID AND INTERPOSED BETWEEN SAID RIGID FRAME AND SAID MOVABLE JAW AND ENGAGING SAID ASSEMBLED FLASK, AND MEANS FOR SUBJECTING SAID PRESS, FLASK AND BELLOWS TO A TEMPERATURE ABOVE THE BOILING POINT OF WATER TO CURE SAID PLASTIC MOLDING COMPOUND AND INCREASE THE DENSITY THEREOF.
 7. METHOD OF MANUFACTURE OF DENTAL BRIDGEWORK AND THE LIKE FROM PLASTIC MOLDING COMPOUNDS SUCH AS ACRYLIC RESINS, WHICH COMPRISES FILLING SUCH PLASTIC INTO THE MOLD CAVITY ABOVE AN ARCH PLATFORM IN A FLASK HAVING PARTS WITH INCLINED COMPLEMENTARY SURFACES, CLAMPING THE PARTS OF SAID FLASK TOGETHER TO CAUSE SAID INCLINED SURFACES TO CAM PARTS THEREBEWEEN TWOARD EACH OTHER TO COMPRESS SAID MOLDING COMPOUND, AND, SUBJECTING SAID FILLED AND CLAMPED FLASK TO A CONFINED SURROUNDING DRY HEAT SOURCE FOR RAISING THE SAME TO ACRYLIC CURING TEMPERATURE TO CAUSE THERMAL EXPANSION OF THE FLASK AND SWELLING OF THE MOLD, THE CLAMPING PRESSURE BEING COMBINED WITH THE THERMAL EXPANSION OF THE FLASK AND SWELLLING OF THE MOLD TO COMPRESS THE PLASTIC THROUGHOUT THE CURING PROCESS AND INCREASE THE DENSITY OF THE CURED PRODUCT. 